Montana Field Guide

For definitions and diagrams of bumble bee morphology please see the Montana State Entomology Collection's Bumble Bee Morphology page. A long-tongued medium-sized bumble bee: queens 18-22 mm in length, workers 13-15 mm. Hair is medium in length and even; Head long, cheek distinctly longer than wide; mid leg basistarsus with back far corner narrowly extended in a spine, hind leg tibia outer surface flat and lacking hair (except fringe) forming a pollen basket; hair of face pale cream-yellow, upperside of head darker yellow; upper side of thorax at front yellow, predominantly black on sides with yellow only within upper half, a black band between the wing bases; T1-4 extensively yellow (sometimes with black hairs intermixed), T5 mostly black. Males 14-16 mm in length; eyes similar in size and shape to eyes of any female bumble bee; antennae long, flagellum nearly 4X length of scape; hair color pattern similar to queens and workers (Colla et al. 2011, Williams et al. 2014).

Across the range, queens reported April to October, workers June to September, males June to October (Williams et al. 2014). In southern Ontario, queens reported May to October, workers June to September, males July to October; earliest record 14 May (Colla and Dumesh 2010, Colla et al. 2011).

Please see the Montana State Entomology Collection's Key to Female Bumble Bees in Montana. Females told from other Montana Bombus by a combination of the hind leg outer surface concave and hairless (except fringe) forming pollen basket; cheek longer than wide; face with pale white or yellow hairs, sometimes cloudy-looking with intermixed black hairs; T2-3 with yellow hair, T3-4 yellow or brownish, T5 mostly black.

Hay fields, near and within woodlands (Plath 1934, Colla and Dumesh 2010, Williams et al. 2014). Hobbs (1966b) indicates this species is confined to prairie in southern Alberta.

Feeds on a variety of flowers, including Astragalus, Carduus, Cirsium, Delphinium, Echium, Eupatorium, Glycyrrhiza, Medicago, Melilotus, Onopordum, Prunella, Rubus, Solidago, Symphyotrichum, Symphytum, Trifolium and Vicia (Plath 1934, Hobbs 1966, Colla and Dumesh 2010, Colla et al. 2011, Williams et al. 2014).

Nests underground (Williams et al. 2014), but otherwise little information. Two queens in southern Alberta established nests about 26 June and 6 July, well after other prairie species of Bombus. One first brood contained 24 pupae (cocoons), and only a single brood of workers was produced. The two Alberta colonies produced 34 and 106 males and queens (Hobbs 1966b). Nests sometime invaded my conspecific queens, who attempt to usurp the nest. Males aggregate outside nest entrances in search of mates, but also attempt to copulate with queens while in the nest (Hobbs 1966b, Williams et al. 2014). Parasitism by cuckoo bumble bees not described.